Apparatus for treating foliate material such as tobacco



Filed Dec. 21, 1965 June 1963 A. PIETRUCCI ET AL 3,386,451

APPARATUS FOR TREATING FOLIATE MATERIAL SUCH AS TOBACCO I 4 Sheets-Sheetl JNVENTORS ANDRE PIE TRUC C! AND GEO/'76 SCHREP June 4, 1968 A.PIETRUCCI ET AL 3,386,451

APPARATUS FOR TREATING FOLIATE MATERIAL SUCH AS TOBACCO Filed Dec. 21,1965 4 Sheets-Sheet 2 INVENTORS ANDRE P/ETRUC'C/ AND GEORG SCHREP June4, 1968 A. PIETRUCCI E 3,386,451

APPARATUS FOR TREATING FOLIATE MATERIAL SUCH AS TOBACCO Filed Dec. 21,1965 4 Sheets-Sheet 5 INVENTORS ANDRE PIE TRUC Cl AND GEORG SCH/7E PJune 4, 1968 A. PIETRUCCI ET AL 3,386,451

APPARATUS FOR TREATING FOLIATE MATERIAL SUCH AS TOBACCO Filed Dec. 21,1965 4 Sheets-Sheet 4 INVENTORS ANDRE P/ETRUCC/ AND GEORG SCHRE P UnitedStates Patent 3,386,451 APPARATUS FOR TREATING FOLIATE MATERIAL SUCH ASTOBACCO Andre Pietrucci, Fleury-les-Aubrais, France, and Georg Schrep,Hamburg, Germany, assignors to Service dExploitation Industrielle desTabacs et des Allumettes, Paris, France, a French public establishmentFiled Dec. 21, 1965, Ser. No. 524,671 14 Claims. (Cl. 131146) ABSTRACTOF THE DISCLOSURE Apparatus for stripping and separating tobaccocomprises several coaxial stripping devices each having a cage and adrum bounding a stripping chamber. The cage and/or the drum of eachstripping device is rotatable and the stripping chambers are concentric,each of these chambers being bounded by at least one rotary wall. Thestripping devices are surrounded by a casing which is associated with afeed device for tobacco and communicates with a takeofi duct forstripped material.

The present invention relates to apparatus for treating foliate materialsuch as tobacco, and is particularly concerned with apparatus forstripping and separating tobacco or other foliate material whichcomprises a plurality of stripping devices of different diameters havingstripping drums rotating about vertical axes and stripping cagesassociated with them.

The co-axial arrangement of the stripping devices of different diametersis to ensure that material before being stripped further passes directlyfrom a smaller stripping device into a larger stripping device.

For this purpose it is known to arrange a plurality of stripping devicesof different diameters one above the other with the stripping drum axesin such manner that the stripping device with the smallest diameter isthe uppermost stripping device and that the subsequent lower strippingdevices have increasingly larger diameters. The mixed material issuingfrom an upper stripping device is projected into a portion of aseparating duct in which mixed material which has already been separatedis conveyed upwardly. A suitable construction of this separating ductenables a good separation effect to be obtained with this type ofconstruction.

An object of the invention is to provide apparatus of the kind referredto above in which the streams of partially or totally stripped materialand of different compositions are prevented entirely or at least to aconsiderable extent from intermixing or crossing each other.

For this purpose the invention provides that the stripping devices aremounted inside each other, that is to say, their stripping chambers areconcentric and comprise at least one rotary wall which may be continuousor discontinuous and which is provided with teeth, wherein at least oneof these chambers is constituted by two concentric walls one of whichrotates and wherein the stripping devices are arranged in a casing whichis connected at the one end to a feed device for foliate material and atthe other end to a take-ofi duct for the leaf material obtained.

A particular embodiment of the invention provides a free space betweenthe stripping cage of one stripping device and the stripper drum of theadjacent larger stripping device, the free space constituting aseparating duct.

Due to the fact that the material is supplied to the first strippingdevice usually only over a small portion of the periphery of the deviceand because of the nature of the stripping operation, the strippedmaterial is not ejected 3,386,451 Patented'June 4, 1968 from thestripper cage in a regular manner. The charging of the circular orpartially circular separating ducts thus varies from one circularsection to the next. Since the flow speed is a function of the charge ofthe separating ducts, undesirable transverse currents occur in theseparating ducts. In order to avoid this, provision is made in oneembodiment of the apparatus according to the invention that at least oneof the separating ducts is divided by partition walls which extendparallel to the general flow direction of the separating air. The heavyparticles carried upwardly in the separating ducts are separated asecond time owing to the fact that the separating ducts terminate in acommon main duct and are con nected through this duct to a commonsuction duct which conveys away only stripped leaf material.

In such apparatus the outer stripping device has the largest diameter.In order to utilise fully the maximum output of this highly eflicientstripping device the feed of material to be stripped can be associatedwith the outer stripping device. The dimensions of the openings in thestripping case and the distances between the beater teeth areadvantageously larger in this outer stripping device than thecorresponding dimensions of the stripping devices with smallerdiameters, in order to obtain in the first stage of tobacco leafstripping leaf portions as large as possible. The mixture which must besubjected to further stripping must be guided to a subsequent interiorstripping device by passing through as large a portion as possible ofthe periphery of the stripper drum. This operation must be effected bymeans of a recycling device for the mixture disposed above the strippingdevices and guiding the mixture from the separating chamber of an outerstripping device towards an inner stripping device. The separating ductof the inner stripping device is advantageously of circular shape sothat the stripped mixture can be ejected from the whole periphery of thestripper cage.

The preferred feed to the largest exterior stripping device permits thestripping devices to be dimensioned favourably in respect of therequired throughput of material; in fact this throughput decreasesdependently upon the decrease of the diameters of the stripping devices.The whole periphery of each stripping device is surrounded by a distinctseparating duct. The separating process in these ducts which is effectedin the region of the stripping devices and which must remove the majorportion of the ribs is not afiected by material which is carriedupwardly and transversely with respect to the ejected material. Theseparating process in the common duct takes place without being affectedby the stripping devices.

In another embodiment the outer wall of one of the stripping devices isthe inner Wall of the next following stripping device, and the radiallyextending teeth can be fixed on the inner or outer surfaces of thesewalls or on both of them simultaneously. This is the case when thecentral stripping device comprises a rotary drum provided with teethturning in a rotary casing having teeth on its outer surface. This isalso the case when the drum of the central stripping device rotates in astationary casing which constitutes the inner wall of the next followingstripping device in which rotate the teeth which are mounted internallyon its outer casing. This is also the case when the central strippingdevice is constituted by a single exterior rotary casing on which areattached teeth sweeping the chamber of the stripping device and teethsweeping the chamber of the next following stn'pping device.

The various combinations may be utilised in accordance withrequirements.

The casing of the apparatus may be merged in respect of the outerstripping device with the outer wall of the device. This wall may bestationary.

The direction of rotation of successive rotary walls may be in the samesense or in the opposite sense.

The invention provides feeder means for the foliate material constitutedby one or more conveyance ducts for foliate material which terminate inthe annular space enclosed between the extensions of the walls of thestripping device or stripping devices to be fed. The duct or ducts maybe pneumatic conveyance ducts, and the air current may traverse thestripping device or stripping devices to be fed from the bottom to thetop.

The duct or ducts may terminate tangentially in the annular space to befed and the rotation of the air may be the same as or opposite to thedirection of rotation of the teeth in the stripping device or devices tobe fed.

In a modification of the invention the foliate material to be strippedis delivered into the annular space through one or more rotary lockgates the blades of which sweep preferably at least a portion of theannular space to be fed.

The foliate material delivered into the space is carried across thestripping chamber under the action of an air current which may be risingand directed towards the base of the chamber.

The embodiment may comprise one separation chamber arranged in the wholeor nearly the whole annular space above the top of a stripping devicetraversed from the bottom to the top and of one or more adjacentstripping devices, said separating chamber being provided in order topermit the light particles to be carried upwardly and the heavierparticles to be guided by gravity towards the adjacent stripping deviceor devices.

For this purpose there may be provided one or more resilient inflatablecushions, for example of annular shape, for adjusting the volume or theconfiguration of the separating chamber.

The embodiment may also comprise a separating chamber arranged in thewhole or nearly the whole annular space between the bottom of astripping device traversed from the top to the bottom by the flow ofparticles and of an adjacent stripping device or stripping devicestraversed by a rising air current, said separating chamber beingprovided in order to permit the ribs to drop by gravity and theparticles which still include rib material to be carried towards thestripping device or devices through which the rising air currenttravels.

The rising air current may be independent of the current which feeds oneof the other stripping devices. It may be obtained by division from thegeneral air stream supplying a plurality of stripping devices.

In the embodiment of the invention the bases of successive strippingdevices may be situated in the same plane or in adjacent planes.

A rising air current may be caused to circulate in a stripping devicefed from above with material to be stripped, the air current beingadjusted so that it carries away only particles of leaf material whichhave been stripped in the course of the downward travel.

Direct lateral ejection of products stripped in a stripping devicetowards a stripping device of larger diameter may be obtained bycompletely or almost completely closing the bottom of the strippingdevice with the smaller diameter and by providing openings orperforations in the intermediate wall between the two stripping devices.The dimensions of the openings or perforations of successivenon-continuous partition walls are determined in proportion to thedimensions of the products to be ejected laterally.

In one embodiment of the invention there may be provided a finalstripping device arranged co-axially with the embodiment, having a solidbottom, an external wall with apertures communicating with theatmosphere, and located under at least one of the stripping devices.

The top of the final stripping device may communicate with theseparating chamber provided under the assembly of the other strippingdevices.

The wall provided with the apertures or the rotary wall provided withteeth of the finishing device, or both may be integral with a wall orwalls of the assembly of the other stripping devices.

There may be provided a control mechanism by means of which the variousstripping devices can be run at different speeds.

One of the advantages of the invention is the small constructionalheight of the apparatus.

Various embodiments of the invention will be described below by way ofexample with reference to the ac companying drawings, in which:

FIG. 1 illustrates apparatus with two concentric stripping devicesseparated by a separation duct, in section along the line II of FIG. 2;

FIG. 2 illustrates a section along the line II-II of FIG. 1;

FIG. 3 illustrates partially in section, apparatus according to theinvention comprising two concentric and adjacent stripping devices andon the same axis, in the lower portion, a stripping device comprising afinal beater device;

FIG. 4 illustrates in section a modification of the apparatus shown inFIG. 1 with a different feed arrangement for the foliate material and adifferent position of the final beater device, and

FIG. 5 illustrates in section apparatus comprising three co-axial andadjacent stripping devices.

In the example illustrated in FIGS. 1 and 2 the apparatus comprises anouter casing or housing 2 and two concentric stripping devices 4 and 21.The outer stripping device 4 is of circular shape with a rotary stripperdrum 6 around which is mounted a stripper cage 8 in a stationaryposition. The latter is supported from above by means of a support 10 inthe form of a plate fixed to the casing 2. A certain number of guidewheels 12 are mounted idly on the periphery of the stripper cage 8; theperipheral ridge of these guide wheels engages the groove of a ring 14.The stripper drum 6 which is fixed at its bottom to this ring 14 isguided by the guide wheels 12 in a horizontal plane of rotation and iscaused to rotate by a friction wheel 16. This wheel 16 is mounted on abearing 18 and is engaged by a motor (not shown) by means of a V-belt20. The inner stripping device 21 is supported at the top of itsvertical shaft 22 in the support 10 by a head bearing 24 which preventsany axial displacement, and at the bottom by a bearing 26, and is setinto rotary motion by means of a V-belt 28 passing over a belt pulley30. In the stripping device 21 a stripper drum 32 rotates in theinterior of a stripper cage 34.

The casing 2 includes three main separating ducts 36, 38, 40 two ofwhich are illustrated in FIG. 1. These ducts terminate in correspondingseparating ducts 42, 43 and 45 (FIG. 2) arranged in zones around themajor portion of the stripping device 4. Between the stripping devices 4and 21, a wall 46 is fixed to the support 10 which delimits ordelineates the separating ducts 50, 55 and 57 between the stripper cage34 and the stripping device 4. These separatmg ducts are connected tothe main duct-s 36, 38, 4G by means of three openings 52 two of whichare visible in FIG. 1, their corresponding ducts 54 and further openings56 being provided in a cap 48. In FIG. 1 ducts 54 are shown for the mainducts 36 and 38. The cross-section of the main ducts increasescontinuously from the bottom to the top. A wall 58 starting at the peakof the cap 48 which extends over all the stripping devices separates allthe main ducts 36, 38, 40 which terminate in their upper zone in acommon exhaust duct 60 which is connected to a fan (not shown in thedrawings). On the right-hand side of FIGS. 1 and 2 a chute 62 which isopen towards the top and which serves for feeding material to bestripped is mounted on the upper portion of the stripping device 4 in afree space between the ducts 36 and 40.

Under the casing 2 a take-off conveyor 64 rotates around a drivingroller 66. A cap 68 fixed by webs 70, 72 to the bearing 26 covers thebelt pulley 30 and a portion of the V-belt 28.

Caps over the rotary members 12, 14, 16 of the stripping device have notbeen illustrated in the drawing for reasons of clarity.

The method of operation of the apparatus is as follows:

A fan (not shown on the drawings) :produces an air stream in thetake-off pipe 60, in the main separating ducts 36, 38, 40 and in theducts 42, 43, 45 and 50, 55, 57. This air stream circulates around thestripping cages 8 and 34 vertically with reference to the plane ofrotation. When the material to be stripped is fed through the chute 62to the rotary stripping device 4 this material is stripped and radiallyejected across'the stripper cage 8 into the rising air stream; itundergoes there by a first separation in the ducts 42, 43, 45 in suchmanner that the ribs from which the leaf material has been removed dropby gravity in counterfiow to the rising air stream on to the take-offconveyor 64. The leaf material or the light mixture is carried awayupwardly by the air stream and guided to the main separating ducts 36,38, 40. In order to explain the sequence of the operation reference ismade below only to the main duct 38 located on the left-hand side inFIG. 1. In the cross-section of this main duct the travelling speed ofthe rising air stream decreases sufliciently for the light leaf materialto be carried away in the direction of the arrow towards the top as faras the take-off pipe 60, whereas the mixture comprising ribs withoutleaf material, ribs with leaf material and leaf material without ribs isdisplaced towards the right, that is to say, towards the inclined wallof the cap 48, and drops under the action of gravity or in the presentcase under the action of suction, into the inner stripping device 21.This dropping is effected across the openings 51, 53 in the direction ofthe broken arrows and entry into the stripping device 21 takes placefrom above.

In this stripping device the mixture is stripped again. The ribs whichare definitely separated from the residual leaf material and the leafmaterial without ribs pass radially across the stripper cage 34 andenter into the rising air stream in the ducts 50. The ribs fall into thetake-off conveyor 64, and the light leaf material is carried awaythrough the duct 54 to the main duct 38. All streams of leaf materialissuing from the ducts 42, 50 are joined in the main duct 38 and areguided through the take-01f pipe 60 to a further manipulation process.In the enlarged cross-section of the main duct 38 there meet at the sametime all other streams of the mixture which return to the strippingdevice 21 through openings 51, 53 and this occurs at a variable returnfrequency until the whole of the mixture is substantially completelyfreed of ribs and all portions which are constituted only by leafmaterial have been removed. The leaf material of the main ducts 36, 40and the corresponding ducts 55, '57 and 43, 45 are treated in the samemanner as described for the separating ducts 38.

In this process the external stripping device 4 is rotated by means ofthe V-belt 20 through the friction force of the guide wheel 16, and thestripping device 21 is set into rotary motion by the V belt 28 and thebelt pulley 30. The rotary speeds of the stripping devices 4 and 21 aresuch that the speed of each stripping device permits the most favourablestripping action to be obtained; thus these two speeds may be different.These different speeds can be controlled by means of an infinitelyvariable change speed device which is not shown in the drawings.

The flow speed of the air stream in the separating ducts and in all themain ducts must also be controllable. This control is effected by meansof dampers or valves, not shown in the drawings, which may be arrangedeither directly on the fan, which is not shown in the drawings, or

at any other appropriate point in the take-off pipe 60 or at any otherpoint of the system.

The embodiment shown in FIGS. 1 and 2 constitutes a practical examplefor a separating system, but which is not necessarily used in order tocarry out the process. The various main ducts and the separating ductsmay alternatively be constructed and arranged in a different appropriatemanner within the scope of the invention. The invention provides alsofor the use of for example three or more stripping devices instead oftwo inserted one into the other in the manner illustrated in FIG. 1. Thewhole system will then comprise an inner stripping device 21 surroundedby one or more circular stripping devices actuated in the same directionor in opposite directions at equal or diiferent rotational speeds. Thestripping devices may alternatively be arranged at different levels andthey may have different constructional heights. Furthermore it is oflittle importance that the control of the stripping devices is differentfrom the control i1lustrated in FIG. 1. The friction wheels 16 may forexample be replaced by gear wheels and the circular stripping device 4may be arranged in a difierent but appropriate manner, for example on arotary shaft.

Similarly the arrangement of the chute 62 serving for feeding materialto be stripped has been illustrated only by way of example. The feed mayalternatively be efiected by means of other systems, such as conveyorbelts, or a lateral pneumatic duct, or by using other auxiliary elementsoperative either from above or in a circular manner. More than one feedpoint may be provided or other feed points may be selected. Similarlythe passage of the mixture from the outer stripping device towards theinner stripping device may alternatively be effected in a differentmanner. Moreover the connection and removal of the ribs may be effectedfor example by a pneumatic duct.

In the example illustrated in FIG. 3 the apparatus comprises a shaft 101held vertically by two fixed bearings 102, 103 and is actuated through apulley 104 by means of a motor and a power transmission not shown. Acore member 105 which is fixed on this shaft embodies on its externalwall teeth 106 and rotates in the interior of a cage constituted by bars107. A second core member 108 guided by the shaft 101 is actuated bymeans of a pulley 109. In its lower portion this core member comprisesteeth 110 which are arranged radially and which rotate in the interiorof a stationary cage constituted by bars 111. The upper portion of thecore member 108 supports the cage which is constituted by the bars 107and which rotates at the same speed as the core 108. Bars 107 areprovided with radial teeth 112 arranged so that they enter betweencounter teeth 113 fixed to the casing 114.

From this description it will now be possible to follow the functioningof the embodiment:

The tobacco leaves or similar foliate material are introduced into thecasing 114 by means of a rotary bladed lock gate 115. Under the actionof the air stream which rises at great speed and which penetrates acrossthe openings 116 between the bars 111 and which is caused by the sectionof a fan (not shown) connected to a take-off pipe or tube 117, theseleaves are carried away upwardly and during the passage through theaction zone of the teeth 112 and counter teeth 113 they are subjected toshocks which cause the leaf material to be detached from the ribs.

The whole of the product obtained which is constituted of pieces of leafmaterial without ribs, pieces of leaf material to which ribs are stillattached and some ribs nearly completely cleaned, is carried away by theair current into the retarding chamber 118 wherein, since thecross-section offered to the passage of the air is increased, aconsiderable slowing down of the air speed is produced. Under the effectof this slowing down the heavier particles, that is to say the piecescontaining ribs, cease to rise and fall down into the stripping deviceconstituted by the core member and the bars 107. In contrast the lightparticles 7 continue to rise in the chamber 118 and are removed throughthe pipe 117.

The heavier particles enter the inner stripping device and are subjectedthere to a renewed stripping process at the end of which the strippedproducts are ejected across the bars 107 and rejoin the flow of tobaccowhich traverses the outer stripping device. Together with the latterthey are separated again in the chamber 118 at the end of which the pureleaf material Will be removed through the pipe 117 whereas the heavierparticles fall back into the inner stripping device. Thus there isproduced a permanent action in the course of which each piece of leafmaterial which is still attached to a rib circulates between the outerstripping device and the inner stripping device and vice versa until therib is Completely cleaned.

When a rib is almost completely cleaned its high density and its smallcarrying surface are such as to permit it to drop between the teeth 106of the interior stripping device and to escape from it through the basethereof. It thus arrives in the final beater or stripping deviceconstituted The ribs ejected from the apparatus are collected by arotating conveyor 119 which may be of the shaker type.

In order to facilitate the control of the air speed and thus theseparation in the chamber 118 there may be disposed in this chamber amember permitting the cross-section of the passage of the air to bevaried. In the example described this member is constituted by aresilient cushion 120 which is connected to a compressed air source andwhich is fixed to the cylindrical wall 121. By varying the quantity ofair contained in the cushion its thickness can be varied and thus alsoits external diameter.

In the example described the feed of leaf material is elfected by asingle lock gate 115. The embodiment may be fed alternatively by meansof two or more gates distributed over the periphery of the casing 114.

Similarly, only a single suction pipe 117 has been illustrated. In facta plurality may be used connected either to the same fan or to differentfans, in order to obtain a better uniformity of distribution of the aircurrent.

In the same way the chamber 118 may be closed partly or completely bymeans of radial closure members 122 thus reducing in the separation zonethe effect of centrifugal forces due to the rotation of the beaters.

The embodiment illustrated in FIG. 4 differs from the preceding one onlyby the position of the final beater or stripping device, the method offeeding leaf material and the circulation of the air current.

According to this modification the lower portion of the casing 114 hasan annular body member into which .terminates tangentially an air inlettube 123. The air travels thus in the casing 114 along a helical path.The foliate material to be stripped is introduced into the tube 123 at apoint not illustrated. Once the material is in the casing 114 it risestherein turning over at the same time and reaches the outer strippingdevice the mobile teeth of which rotate preferably in the same directionas the air current. Thereafter successive beating and separating isefiected as indicated above, until the ribs are almost completelycleaned.

The almost completely cleaned ribs are discharged slowly into the innerstripping device and finally fall into the lower portion of this devicewhere the final stripping device is located which is constituted by theteeth 110 and the bars 111. When the air path is arranged so that thequantity of air admitted into the pipe 123 is smaller than the quantitywhich leaves through the pipe 117, air

8 enters through the openings 116 between the bars 111. This air cannotprevent the ejection of the ribs; in fact it prevents the removal of thesmall particles of leaf material which have been freed in the finalstripping device and which will be carried away towards the duct 117across the stripping devices.

FIG. 5 illustrates a second modification of the apparatus and comprisesthree co-axial stripping devices. The foliate material to be strippedenters into the apparatus through the tube 123 which terminatestangentially in the annular space 124 which acts in the same way as acyclone. The outlet opening of this cyclone communicates directly with afirst stripping device constituted on the one hand by teeth 106 fixed tothe core member actuated by the pulley 109, and on the other hand by acage formed by the bars 107. This cage is fixed to the core member 125which is attached to the shaft 101. It rotates at the same speed as thisshaft.

The foliate material admitted into this first stripping device issubjected to a first stripping action at the end of which the freedproducts are removed partly by lateral ejection across the bar cage 107and partly through openings provided in the top of the cage. The tobaccoparticles which arrive in the retarding chamber 118 are separated thereinto particles of pure leaf material which are removed from theapparatus through the pipe 117, and into ribs and particles of leafmaterial to which ribs are still attached which fall back by gravityinto the second and third stripping devices.

In principle the construction of the second stripping device is notsubstantially different from that of the first device. It comprisesteeth 126 fixed on bars 107 and bars 127 connected to an annular member128 actuated by one or more friction wheels 129. The particles freed inthe second stripping devices are ejected laterally across the cageformed by the bars 127 and enter into the third stripping device,constituted by the teeth 112 fixed to the bars 127, and counter teeth113 fixed to the casing 114.

At the level of the lowermost teeth 112 the casing 114 comprisesrelatively small apertures limited by .the bars 111 in such manner thatthe final cleaning of the ribs is ensured. The air entering throughthese apertures ensures that the light particles freed in the finishingzone and in the third chamber are carried away towards the chamber 118.

It will be seen that the supply of leaf material may be efiected asindicated in the embodiment illustrated in FIG. 3. In this case theannular space 124 is open to the atmosphere and the foliate materialmust be applied in the vicinity of its inlet region by a conveyor. Inorder to ensure a better distribution of the tobacco supplied there maybe utilised moreover two or more conveyors delivering foliate materialto points distributed over the periphcry of the inlet region of thespace 124.

Normally an embodiment such as described with reference to the variousmodifications illustrated in FIGS. 3, 4 and 5 is sufficient to ensurecomplete stripping of the tobacco introduced. However, when very long orvery light tobacco is treated, or when operation takes place at a highrate of throughput, accumulations of ribs and leaf material are formedin the chamber 118 which fall back into the chambers causing anobjectionable degradation of the leaf material. In order to avoid thisdisadvantage the throughput of separating air can be regulated in suchmanner that these accumulations cannot form. It may also be found thatproducts which contain ribs are carried away with the particles of pureleaf material; these products are largely complete or almost completeleaves. It is then sutficient to arrange between the pipe 117 and theapparatus or device intended to receive pure leaf material, one or moreseparating chambers of a classic type in which the particles of leafmaterial which still comprise ribs are separated from the pure leafmaterial, in order to be reintroduced into the flow of foliate materialadmitted to the apparatus for the first time.

In any embodiment the stripping effect in one of the stripping devicesis a function of the relative speed existing between the two casingslimiting the stripping device in question. This relative speed can beobtained either by causing the two casings to rotate in oppositedirections or by causing them to rotate at the same time but atdifferent speeds or even by causing them to rotate as a unit. The choicebetween these various embodiments depends on the type of tobacco to bestripped and on .the degree of stripping which must be obtained.

What we claim is:

1. An apparatus for stripping and separating tobacco or other foliatematerial comprising a plurality of coaxial stripping devices each havinga stripper cage anda stripper drum delineating a stripping chamber, saidchambers being concentric and at least one of said cage and said drumbeing a rotary member and at least one of such chambers being delineatedby concentric walls of which at least one is rotary, a casingsurrounding said stripping devices, a feed device for foliate materialand a take-off duct for the leaf material obtained communicating withsaid casing.

2. Apparatus according to claim 1, wherein a free space is providedbetween the stripper cage of one stripping device and the stripper drumof the adjacent larger stripping device, said space being arranged toconstitute a separating duct.

3. Apparatus according to claim 2, wherein partition walls extendingparallel to the main direction of flow of the separating air devide atleast one of the separating ducts.

4. Apparatus according to claim 2 further comprising a common take-offduct and a common main duct connecting said separating ducts with saidtake-01f duct.

5. Apparatus according to claim 1 wherein said feed device for foliatematerial is associated with the external stripping device.

6. Apparatus according to claim 2 further comprising means located abovesaid stripping devices for recycling mixture from a separating duct ofan interior stripping device towards an interior stripping device.

7. Apparatus according to claim 1 wherein the exterior delineating wallof a stripping device is the interior delineating Wall of the nextfollowing stripping device.

8. Apparatus according to claim 7 wherein the central stripping devicecomprises a rotary drum provided with teeth turning in a cage providedwith teeth at least on its exterior surface.

9. Apparatus according to claim 7 wherein the walls delineating thestripping chamber of at least one of said stripping device are providedwith extensions delineating an annular space and at least one conveyingduct for feeding foliate material terminate on said annular space.

10. Apparatus according to claim 7 further comprising means for creatinga rising air current for carrying away the discharged foliate material.

11. Apparatus according to claim 7 further comprising an annularseparation chamber above at least one of said stripping devices therebypermitting light particles to be carried upwardly and heavier particlesto drop by gravity towards at least one adjacent stripping device.

12. Apparatus according to claim 11 further comprising at least oneinflatable resilient cushion in said separating chamber for adjustingthe volume thereof.

13. Apparatus according to claim '16 further comprising an annularseparating chamber below at least one .of said stripping devices therebypermitting ribs to drop by gravity and particles of leaf material to becarried away towards the stripping device or devices traversed by therising air current.

14. Apparatus according to claim 7 further comprising a final strippingdevice coaxial with said apparatus, and having .a solid bottom, and anexternal wall provided with apertures communicating with the atmosphere,and located under at least one of said stripping devices.

References Cited UNITED STATES PATENTS 1,024,832 4/1912 Cox 241511,977,771 10/1934 McMahan 131l46 X 2,050,765 8/1936 Rundell 131146 X2,474,314 6/1949 Koehne 241-51 X 3,046,998 7/1962 Mortimer 131l463,229,698 1/1966 Johansson et al. 131- 146 ALDRICH iF. ME'DBERY, PrimaryExaminer.

